Many conventional devices are available for obtaining blood samples from a patient for laboratory testing. For example, a conventional syringe and a hypodermic needle are often used as is well known to those skilled in the art.
When multiple samples are needed for laboratory tests, traditionally, a blood collection needle is used. Generally, such devices include a pair of needles disposed in line axially on a central hub or housing. These needles are generally provided in a tube-holding device, typically a hollow cylindrical body with open ends. The hub of the blood collection needle is generally attached to one end such that one needle extends into the cylindrical body, while the other needle extends axially beyond the end of the cylindrical body for percutaneous introduction into a patient.
Conventional vacuum specimen tubes are then inserted into the other end of the cylindrical body. The rubber stopper of the specimen tube is punctured by the needle inside the cylindrical body, creating a continuous passage from the percutaneous needle tip to the specimen tube. Thus, after the blood collection needle has been introduced into a patient, a series of specimen tubes may be inserted into the cylinder to collect separate samples for testing.
One of the problems related to the use of such traditional devices is hemolysis. When the specimen tube is inserted into the blood collection device, the fixed vacuum of the tube draws blood through the passage quickly. The uncontrolled flow of blood caused by the force of this vacuum often causes red blood cells to shear and break down. Potassium is released from the cells into the blood fluid, creating inaccuracies in the laboratory tests performed on the samples.
Additionally, such conventional devices present problems in obtaining samples from patients having poor peripheral access, such as young and elderly patients whose veins are smaller or more susceptible to collapse.
Attempts have been made to modify these conventional blood collection devices to respond to these problems. For example, U.S. Pat. No. 5,133,362, by Moss, discloses a blood collection needle which uses a smaller gauge needle for introduction into the patient than is used for the specimen tubes. The device uses such smaller gauge needles to provide improved peripheral access, while also slowing blood flow through the needle to reduce hemolysis. As will be shown below, however, this device fails to address the viscous effects of blood flow through the needles, which contributes substantially to hemolysis in the resulting blood samples.
Thus, there is a need for an apparatus for drawing blood from a patient which substantially reduces the risk of hemolysis as blood is drawn into vacuum specimen tubes.
There is also a need for an apparatus for drawing blood which provides improved introduction into patients having poor peripheral access without the associated higher likelihood of hemolysis.